Stop jumping at shadows.
The Crown will not attempt to adduce any evidence of the sort that is now being debated.
With respect, it is, to them, just a 5hitty use mobile phone while driving offence. It is not a life offence or one where they have nabbed a feared criminal mastermind. They will not commit too many resources to the prosecution of the matter if indeed the OP decides to contest the ticket.
The evidence the Crown will adduce I expect will be limited to the 2 coppers saying "I saw xyz".
The OP would then both give and call evidence to counter the eye witness evidence of the 2 coppers with a view to establishing that their eye-witness account is mistaken.
Quite simple really and done in 1/2 a day.